Preprints
https://doi.org/10.5194/acp-2021-51
https://doi.org/10.5194/acp-2021-51

  03 Feb 2021

03 Feb 2021

Review status: this preprint is currently under review for the journal ACP.

Aerosol absorption in global models from AeroCom Phase III

Maria Sand1, Bjørn H. Samset1, Gunnar Myhre1, Jonas Gliß2, Susanne E. Bauer3,4, Huisheng Bian5,6, Mian Chin6, Ramiro Checa-Garcia7, Paul Ginoux8, Zak Kipling9, Alf Kirkevåg2, Harri Kokkola10, Philippe Le Sager11, Marianne T. Lund1, Hitoshi Matsui12, Twan van Noije11, Samuel Remy13, Michael Schulz2, Philip Stier14, Camilla W. Stjern1, Toshihiko Takemura15, Kostas Tsigaridis4,3, Svetlana G. Tsyro2, and Duncan Watson-Parris14 Maria Sand et al.
  • 1CICERO Center for International Climate Research, Oslo, Norway
  • 2Norwegian Meteorological Institute, Oslo, Norway
  • 3NASA Goddard Institute for Space Studies, New York, USA
  • 4Center for Climate Systems Research, Columbia University, New York, USA
  • 5Maryland Univ. Baltimore County (UMBC), Baltimore, MD, USA
  • 6NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 7Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Gif sur Yvette Cedex, France
  • 8NOAA, Geophysical Fluid Dynamics Laboratory, Princeton, NJ, USA
  • 9European Centre for Medium-Range Weather Forecasts, Reading, UK
  • 10Atmospheric Research Centre of Eastern Finland, Finnish Meteorological Institute, Kuopio, Finland
  • 11Royal Netherlands Meteorological Institute, De Bilt, the Netherlands
  • 12Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan
  • 13HYGEOS, Lille, France
  • 14Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, UK
  • 15Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka, Japan

Abstract. Aerosol induced absorption of shortwave radiation can modify the climate through local atmospheric heating, which affects lapse rates, precipitation, and cloud formation. Presently, the total amount of such absorption is poorly constrained, and the main absorbing aerosol species (black carbon (BC), organic aerosols (OA) and mineral dust are diversely quantified in global climate models. As part of the third phase of the AeroCom model intercomparison initiative (AeroCom Phase III) we here document the distribution and magnitude of aerosol absorption in current global aerosols models and quantify the sources of intermodel spread. 15 models have provided total present-day absorption at 550 nm, and 11 of these models have provided absorption per absorbing species. The multi-model global annual mean total absorption aerosol optical depth (AAOD) is 0.0056 [0.0020 to 0.0097] (550 nm) with range given as the minimum and maximum model values. This is 31 % higher compared to 0.0042 [0.0021 to 0.0076] in AeroCom Phase II, but the difference/increase is within one standard deviation which in this study is 0.0024 (0.0019 in Phase II). The models show considerable diversity in absorption. Of the summed component AAOD, 57 % (range 34–84 %) is estimated to be due to BC, 30 % (12–49 %) is due to dust and 14 % (4–49 %) is due to OA, however the components are not entirely independent. Models with the lowest BC absorption tend to have the highest OA absorption, which illustrates the complexities in separating the species. The geographical distribution of AAOD between the models varies greatly and reflects the spread in global mean AAOD and in the relative contributions from individual species. The optical properties of BC are recognized as a large source of uncertainty. The model mean BC mass absorption coefficient (MACBC) value is 9.8 [3.1 to 16.6] m2 g−1 (550 nm). Observed MAC values from various locations range between 5.7–20.0 m2 g−1 (550 nm). Compared to retrievals of AAOD and absorption Ångstrøm exponent (AAE) from ground-based observations from the Aerosol Robotic Network (AERONET) stations, most models underestimate total AAOD and AAE. The difference in spectral dependency between the models is striking.

Maria Sand et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-51', Anonymous Referee #1, 03 Mar 2021
  • RC2: 'Comment on acp-2021-51', Gregory L. Schuster, 24 Mar 2021

Maria Sand et al.

Maria Sand et al.

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Short summary
Absorption of shortwave radiation by aerosols can modify precipitation and clouds, but are poorly constrained in models. 15 different aerosol models from AeroCom Phase III have reported total aerosol absorption and for the first time 10 these models have reported in a consistent experiment the contributions to absorption from black carbon, dust and organic aerosol. Here, we document the model diversity in aerosol absorption and compare with observations.
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